Ink drop writer nozzle



y 1970 P. COLE CHI 3,512,172

nix DROP WRITER NOZZLE Filed Aug. 22. 1968 2 Sheets-Sheet 1 SOURCE 15 OF L SYNC.

ELECTRO- SIGNALS. MECHANICAL J INK TRANSDUCER UNDER IO 1/ PRESSURE VIDEO 24 l4 SIGNAL SOURCE 22 FIELD 32 POTENTIAL [34 g SOURCE 38 WASTE 4 CATCHER 0 4e 4O 56 54 52 5Q l 5 FIG. 2

I N VEN TOR. PAUL COLECC Hl ATTORN EYS.

May 12, 1970 Filed Aug. 22, 1968 P. COLECCHI INK DROP WRITER NOZZLE FIG. 5

FIG. 3

FIG.4

2 Sheets-Sheet 2 INVENTOI? PAUL COLECCH! United States Patent Int. Cl. G01d 15/18 US. Cl. 346-75 6 Claims ABSTRACT OF THE DISCLOSURE A nozzle construction for an ink drop Writer is provided wherein in order to obtain the emission of uniformly sized and spaced droplets in the fluid which is emitted from the ink drop writer nozzle, the fluid stream passing through the nozzle is mechanically modulated by applying successive mechanical pulses to a housing holding the nozzle which stretch the housing and thereby reduce its diameter which in turn applies compressive pressure to the nozzle. This is accomplished by using a pair of crystals mounted on the housing and which when excited electrically expands axially to stretch the housing.

BACKGROUND OF THE INVENTION This invention relates to apparatus for printing information conveyed by video signals using ink drops deposited on a writing medium, and more particularly to an improved nozzle construction which is used therein.

Apparatus has been developed for making a record on a writing medium of the information represented by video signals, by generating a stream of ink drops, applying a charge successively on each of these ink drops in response to a received video signal, then, directing these ink drops in a path between two parallel conductive plates, which path terminates on a writing medium. A bias potential is applied to these plates with the result that the ink drops are deflected so that they reach the writing medium they provide a representation of the information contained in the video signals. The general apparatus employed for producing the ink drops consists of an ink reservoir in which there is ink under pressure. The ink reservoir feeds a pipe which is connected to a nozzle. An electromechanical transducer is employed to vibrate the pipe and a nozzle at some suitable high frequency which causes the ink to be ejected from the nozzle in a stream which shortly thereafter breaks into individual drops.

The mechanism usually used is one which either actually vibrates the nozzle or which consists of a piezoelectric crystal cylinder having a central opening through which the nozzle is inserted. The crystal is cemented to the nozzle and is polarized so that when it is excited, it expands and contracts radially to apply mechanical compression pulses to the nozzle.

The mechanical compression of the tube provides better control of drop formation and drop spacing than the vibration of the tube. However, difficulties have been experienced in attempting to contain a satisfactory mechanical coupling of tube and crystal which insures a sufficient compression of the tube to obtain proper drop spacing and formation. Also, it does happen that even though a proper junction of tube and crystal is achieved, due to the high frequency operation (on the order of 30 to 60 kHz.) which is required, a fracture or parting of crystal and tube often occurs in the area at which the two are cemented together, after a period of use.

OBJECTS AND SUMMARY OF THE INVENTION An object of this invention is the provision of an improved arrangement for coupling the electromechanical device to an ink jet nozzle.

Another object of the present invention is the provision of a construction whereby the electromechanical transducer can constrict an ink jet nozzle without the requirement for being cemented thereto.

Yet another object of the present invention is to provide an improved construction for an ink jet nozzle for use in a device of the type described.

These and other objects of the invention are achieved by an arrangement wherein the electromechanical devices, such as piezo-electric crystals, have the ink nozzle inserted through openings therein. However, the crystals, are supported by structures at either end which apply compressive forces thereto. The crystals are polarized so that when a voltage is applied across them they expand or contract axially. This applies a mechanical force against the support structures on both ends, which in turn serves to elongate and thereby constrict the nozzle. No problems arise either in securing the proper attachment of the crys tals to the nozzle or in maintaining such attachment under conditions of operation.

The novel features of the invention are set forth with particularity in the appended claims. The invention will best be understood from the following description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic arrangement for ink drop recording in accordance with the prior art, which is shown for the purposes of explanation.

FIG. 2 is an exploded view of an assembly of the parts which are used with an ink nozzle in accordance with this invention.

FIG. 3 is an assembly for an ink nozzle in accordance With this invention.

FIG. 4 is a rear view of the assembly shown in FIG. 3; and

FIG. 5 is a front vieW of an ink nozzle assembly in accordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is provided in order to afford an understanding of the environment for this invention. It illustrates schematically the known ink drop recording apparatus. This apparatus comprises an ink reservoir 10 in which the ink is placed under pressure. Tubing 12 connects the ink reservoir to a terminating nozzle 14. An electromechanical transducer 16 is usually employed and it either vibrates the tubing or compresses it, in response to output signals from a source of sync signals 18. Near the tip of the nozzle 14, the ink is emitted as a solid stream 20 which, however, shortly thereafter breaks into drops, such as 22. A charging tunnel 26, consisting of a conductive tube, is shown open for the sake of illustration, is positioned at the location at which a stream of ink begins to break up into drops. The video signal source 24 has its output connected to the conductive tubing 12 and to the charging tunnel 26, as a result of which each drop 22 will assume a charge whose amplitude is proportional to the video signal applied between the charging tunnel 26 and the tubing 12 at the time that the drop is breaking away from the ink stream within the tubing 26.

The charged drops then continue in a path toward the moving paper 36. However, before they reach the paper, they pass between two spaced parallel plate electrodes, 30, 32, to which a fixed potential is supplied from a field potential source 34. The charged drops are caused to enter an electric field established between the electrodes 30, 32 as a result of which each drop is deflected from the path it would take in the absence of the electric field, an amount determined by the charge thereon. Trough 38 is positioned to catch drops to a waste catcher 40. Ac

cordingly, as the paper 36 is continuously moved, a line is drawn thereon whose shape or curvature is determined by the signals from the video signal source.

Alphanumeric characters as well as lines or curves may be drawn by this apparatus. In effect, therefore, the recording on paper is representative of the information conveyed by the video signals.

FIG. 2 is a view of the parts which are used in making the nozzle in accordance with this invention. This draw ing should be considered together with FIG. 3, FIG. 4, and FIG. which are respectively views of an assembly in elevation and from the rear and front sides.

An assembly in accordance with this invention will include a nozzle housing 40, into which there is inserted a tubing 42. At the front end of the nozzle housing 40, designated by the reference numeral 40A, there is attached a. watch jewel 44 having a hole drilled in the center therein. The jewel can be attached by staking or by cementing. Adjacent the front end portion 40A is a flared portion of the housing 403. This has a larger outer diarneter than the portion 40A. The flared portion 40B is followed by a central portion 40C which is used for supporting electromechanical crystals. Adjacent the support portion 40C is a terminating portion of the housing 40D. This has its diameter enlarged so that it can be engaged by a standard size nut. Provision for engaging the nut is afforded by threads 40E on the end of the terminating portion 40D.

Metal tubing 42 is inserted into the housing 40. An opening in the center portions 40C, 40D of the housing 40 is large enough to enable the tubing 42 to be inserted therein. This opening is reduced in diameter within the flared portions 40B and 40A to provide a seat for the jewel 44. The opening in the center of the housing is represented by the dotted lines shown on the housing structure 40.

The housing is made of a conductive material such as metal. The tubing 42 is pushed into the housing only part way and is then fixed into position by applying solder between it and the end of the housing 40E.

The remaining structures shown to the left of the tubing 42 in FIG. 2 is slipped over the housing 40 in the order in which they appear. Thus, first comes an electromechanical crystal 46, such as a piezo-electric crystal which is placed abutting the flanged portion 40B of the housing. Adjacent the piezo-electric crystal 46 is a contact terminal 48. Adjacent to contact terminal is a second piezo-electric crystal 50. Adjacent the second piezo-electric crystal is a washer 52. Adjacent the washer 52 is an L-shaped mounting support 54. These are all held in position by the threaded portion of support 54 and by a lock nut 56.

The crystals 46, 50 have the surfaces which respectively contact the flanged portion 40B, the contact 48, and the washer 52 plated to act as electrodes. They are polarized so that when an electrical signal is applied thereacross they will expand, or contract, axially and not radially.

As shown in FIG. 3, the signals from the source of sync signals 18 is applied to two contact terminals, one of them being the terminal 48, and the other being a terminal 58. Terminal 58 may be better seen in FIG. 4, which is a side view of the improved assembly. The terminal is attached to the support bracket by means of a screw 60, and is positioned adjacent to the nut 56.

FIG. 5 shows a front view of the nozzle assembly. In operation, when the sync signals from the source are applied to the contact terminals 48, 58, signals are applied to the inner surfaces of the two crystals 46, 50 by the contact 48, and to the outer surfaces of the crystals by the circuit including the contact 58 which connects with the support member 54, which is made of metal and therefore is conductive, and through the washer 52 and flange 40B to the contact surfaces on the outer ends of the respective crystals 46, 50. Of course, the contact 48 is supported between the two crystals so that no part of it touches the portion of the housing 40C.

The crystals will expand and contract in response to the electrical signals in an axial direction, thereby pushing at one end on the flange 40B and at the other end on the end portion 40D. This elongation of the housing causes it to reduce the diameter of the opening in the center thereof which in turn applies a constricting action on the tubing 42 which extends within the housing. The uniform constrictions of the tubing 42, extending over a substantial region thereof, results in more uniform drop formation and drop spacing in the ink stream after it leaves the nozzle, than has been achieved heretofore with a crystal directly constricting the tubing. As a result, better performance of the ink drop writer is achieved.

By way of illustration of the dimensions of the housing, and not to serve as a limitation thereon, the overall length of the nozzle housing 40 in an embodiment of the invention which was built and operated, was .562 inch. The section on which the crystals were mounted was .218 of an inch. The lengths of the respective sections 40A and 40B were on the order of .0725 inch. The sections 40A and 40C respectively had a diameter on the order of .093 and .078 inch. The section 40B had a radius of .141 inch. The diameter of the section 40B was .0990 inch. The opening through the sections 40B, 40C and 40D was made by a number 59 drill. A No. 72 drill was used to make the opening through the section 40A and partially into 40B.

There has accordingly been described above a novel construction for an ink jet nozzle assembly which affords a uniform drop size spacing, and which avoids problems found in the prior art ink jet nozzle assembly.

Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art.

What is claimed is:

1. In an ink drop writer of the type wherein ink drops are formed by applying periodic constrictions to a nozzle through which said ink flows, the improvement in said nozzle construction comprising tubing through which said ink flows, said tubing having one end through which ink is emitted, a housing having an opening therethrough for receiving a portion of said tubing extending from said one end, said opening in said housing extending therethrough and terminating in a second opening to permit ink from said tubing to be emitted from said housing, and means for periodically elongating said housing for reducing the diameter of the opening therein in which said tubing is inserted for applying periodic constrictions to said tubing whereby ink drops are formed in the ink which is emitted from said housing.

2. In an ink drop writing system as recited in claim 1 wherein said means for periodically elongating said housing includes electromechanical transducer means polarized to expand axially in response to the application of a voltage pulse thereto, means for supporting said electromechanical transducer means securely on said housing, and means for applying voltage pulses to said electromechanical transducer means when it is desired to form ink drops.

3. A nozzle construction for an ink drop writing system comprising a housing having an opening therethrough;

a nozzle having one end through which ink is emitted when applied to the other end; means for inserting said nozzle for a distance from its one end into the opening in said housing;

electromechanical transducer means having an opening therein toafford the mounting thereof on said housing, said electromechanical transducer means being polarized to expand and contact axially in response to the application of a voltage thereto;

restrictive means on said housing for securely supporting said electromechanical transducer means at its opposite axial ends; and

means .for applying voltage pulses to said electromechanical transducer means to cause it to expand and contract axially to apply axial pressures to said housing whereby said housing will constrict the size of the opening therethrough and the nozzle therein to cause drops to be formed in the stream of ink which is emitted from said housing.

4. An ink drop Writing system as recited in claim 3 wherein the electromechanical transducer means com prises a pair of piezoelectric crystals having an opening therethrough for affording the insertion of said nozzle housing therethrough, and wherein said means for supporting said electromechanical transducer means on said housing securely for applying elongating pulses thereto upon the application of voltage pulses to said electromechanical transducer means includes walls defining a flange at one end of said housing, said electromechanical means abutting said flange, and a nozzle supporting means means for attaching said nozzle supporting means to said housing and in abutting relationship with the side of electromechanical transducer means opposite to the one which is abutting said flange means.

5. A nozzle structure for emitting ink drops comprising:

tubing having one end through which ink is emitted when it is applied to the other end of said tubing;

a nozzle housing having an opening extending therethrough;

means for attaching said tubing to said housing with said one end of said tubing extending into the opening of said housing;

piezo-electric crystal means mounted on the outside of said housing, said piezo-electric means being polarized to expand and contract axially in response to the application of voltage pulses thereto;

means holding said piezo-electric means on said housing for causing said housing to expand or contract axially in response to axial expansions and contractions of said piezo-electric means whereby constricting forces are applied to said tubing within said housing; and

means for applying voltage pulses to said piezo-electric means.

6. Apparatus as recited in claim 5 wherein said piezoelectric means comprise two toroidal shaped piezo-electric crystals, and said means for holding said piezo-electric means on said housing for expanding and contracting said housing axially in response to axial expansions and contractions of said piezo-electric means includes a flange adjacent to one end of said housing against which said one side of said piezo-electric means abuts, a support bracket, said support bracket having an opening to afford insertion of the other end of said housing therethrough until it abuts the other end of said piezoelectric means, and nut means threadably mounted on said housing for holding said support bracket means in abutting relation with the other end of said piezo-electric means.

References Cited UNITED STATES PATENTS 3,281,860 10/1966 Adams et al 346- 3,334,350 8/1967 Adams 346-75 JOSEPH W. HARTARY, Primary Examiner US. Cl. X.R. 346- 

